Connector suitable for high-speed transmission of signals
This application is a continuation of application Ser. No. 07/253,589, filed Oct. 5, 1988 now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to a connector suitable for the high-speed transmission of signals. 
     In parallel with the increase in the operation speed of a computer or similar electronic apparatus, a demand for a connector capable of repeating high-speed signals with accuracy is increasing. The high-speed signals refer to those signals having frequencies above gigahertz order, for example. 
     An example of prior art connectors elaborated to meet the above demand is disclosed in Japanese Patent Disclosure (Kokai) No. 60-68570. The connector shown and described in this Patent Disclosure, however, has a disadvantage that the frequencies of signal with which their waveforms can be transmitted accurately are limited, as discussed in detail later. 
     SUMMARY OF THE INVENTION 
     An object of the invention is, therefore, to provide a connector free from the above-mentioned disadvantage of the prior art connector. 
     According to an aspect of the invention, there is provided a connector which comprises: a plurality of coaxial pins each having an inner conductor connected to a signal line of a coaxial cable, an outer conductor connected to a ground line of the coaxial cable, and an insulator providing electrical insulation between the inner conductor and the outer conductor; a housing having a first surface and a plurality of first bores extending from the first surface for receiving the coaxial pins, each of the first bores having a predetermined length; a flat member made of a good electrically conductive material and disposed in the housing to face the first bores; first arms formed by cutting and raising those portions of the flat member which are associated one-to-one with the first bores, the first arms being electrically connected to the outer conductors of the coaxial pins; a plurality of second bores extending toward the flat member from a second surface of the housing which is opposite to the first surface and receiving ground pins; second arms formed by cutting and raising those portions of the flat member which are associated one-to-one with the second bores, the second arms being electrically connected to the ground pins. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other features and advantages of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings in which: 
     FIG. 1 is a fragmentary perspective view of a prior art connector; 
     FIG. 2 is a cross-sectional view of a first embodiment of the invention; 
     FIG. 3 is a perspective view of a thin metal plate used in the embodiment of FIG. 2; 
     FIG. 4 is a perspective view of a general construction of a connector in accordance with the invention; and 
     FIG. 5 is a cross-sectional view of a thin metal plate applicable to a second embodiment of the invention. 
     In the drawings, the same reference numerals represent the same structural elements. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     To better understand the invention, a brief reference will be made to a prior art connector as disclosed in the above-mentioned Patent Disclosure referring to FIG. 1. The connector includes conductive plates 20 and 21 which are combined in a lattice configuration to form a number of prismatic hollow spaces 22. 
     Coaxial pins (not shown) are connected to one ends of coaxial cables (not shown) and inserted into the spaces 22 from above as viewed in the figure, respectively. The coaxial pin received in any one of the spaces 22 is held between contact portions 23. On the other hand, signal pins are individually inserted into deep recesses of the coaxial pins from below through openings 24, whereby the signal pins and signal lines of the coaxial cables are individually electrically interconnected. Further, ground pins are inserted into openings 25 and held between contact portions 26 of the plates 20 and 21. This provides electrical connection between a ground line of each of the coaxial cables and an associated one of the ground pins along a path which is indicated by an arrow A in FIG. 1. In this manner, numerous coaxial pins are inserted from above while numerous signal pins and ground pins which alternate with each other are inserted from below so as to set up electrical connection between the signal lines of coaxial cables and the signal pins associated with the signal lines. At the same time, each of the ground lines of the coaxial cables is electrically connected to an associated one of the ground pins. The connector with such a configuration is ready to transmit signals. 
     The prior art connector described above has a disadvantage that in those portions where the plates 20 and 21 combined in a lattice configuration and held at ground potential make contact with each other, impedance is developed due to such a contact. The connector has another disadvantage that the contact portions 23 of the plates 20 which the coaxial pins individually contact and the contact portions 26 which the ground pins individually contact are electrically interconnected by the conductive path A having a substantial length. For these reasons, the frequencies of signals with which their waveforms can be transmitted with accuracy are limited. 
     Referring to FIG. 2, a first embodiment of the invention is shown and generally designated by the reference numeral 1. The right half of the figure shows those positions where coaxial pins 3 and signal pins 7 are inserted while the left half shows those positions where ground pins 8 are inserted. 
     The connector 1 comprises a coaxial pin housing 5 provided with a number of deep bores 4. The pins 3 connected to respective coaxial cables 2 are inserted into the respective bores 4 of the housing 5. A number of signal pins 7 and ground pins 8 are implanted in and studded on a substrate 6. The signal pins 7 engage with the respective pins 3. A ground pin housing 11 is formed with a group of bores 9 and another group of bores 10 which receive the pins 7 and the pins 8, respectively. A single thin plate of metal 12 is held between the housings 5 and 11 and extends substantially perpendicular to the direction of insertion of the pins 3, 7 and 8. 
     The plate 12 is cut and raised to form resilient pieces or arms 13 at those positions of the plate 12 where the pins 3 inserted in the bores 4 from above intersect the plate 12. As shown in the figure, the arms 13 extend in the opposite direction to the direction in which the pins 3 are inserted into the bores 4. Each of the pins 3 is formed with circumferential recesses 3b on its outer periphery. When the pins 3 are received in the bores 4, they are individually resiliently retained by the arms 13. The plate 12 are also formed with openings 14 in the vicinity of the arms 13 so that the pins 3 are retained with their tips 3a penetrating the plate 12 through those openings 14. In this manner, coaxial pin contacts 17 are formed in one-to-one correspondence with the pins 3. 
     The diameter of each of the bores 4 is small enough to allow the pin 3 to be inserted smoothly but closely. As shown in the figure, the depth of each of the bores 4 is about four times greater than the height of each of the arms 13. Such a configuration causes each of the pins 3 to be inserted between associated ones of the arms 13 perpendicularly from above as viewed in the figure. In other words, it prevents the pin 3 from being inserted with the pin 3 inclined or shifted to the side. As a result, the arms 13 are safeguarded against damage in the event of insertion of the pins 3. When the pins 3 are inserted into the bores 4, the pins 3 are brought into positive contact with the arms 13 at their outer periphery while the pins 3 are surely retained by the arms 13. 
     The pins 7 are inserted into the pins 3, which are received in the openings 14 and retained by the arms 13, through the bores 9 from the tips 3a of the pins 3. This provides electrical connection between the signal lines of the cables 2 and the pins 7. 
     The pins 8 are inserted into the bores 10 simultaneously with the insertion of the pins 7 into the bores 9. The plate 12 is cut and raised at those positions of the plate 12 where the pins 8 penetrate so as to form resilient arms 15. The arms 15 extend in the opposite direction to the direction of insertion of the pins 8. Each of the pins 8 is resiliently retained by associated ones of the arms 15 to form ground pin contacts 18. In this instance, the tips 8a of the pins 8 penetrate openings 16 which are defined between the arms 15. 
     A prerequiste with the plate 12 is that the arms 13 and 15 be capable of retaining the pins with a sufficient degree of resilience and have a sufficient electrical-conductivity with respect to high frequencies. To meet this prerequisite, the plate 12 may be implemented by a plate of stainless steel plated with gold by way of example. 
     As shown in FIG. 3, the contacts 17 and 18 are located in close proximity to each other so that the outer surfaces of the pins 3 and those of the ground pins 8 are electrically interconnected at the shortest distance. 
     In the embodiment, the pins 3a are retained with their tips 3a penetrating downward the openings 14 of the plate 12. Alternatively, an arrangement may be made such that the pins 7 penetrate the plate 12 upward through the openings 14 into the pins 3 whose tips 3a are located above the openings 14. Likewise, the ground pins 8 may be reduced in length such that their tips 8a are positioned below the plate 12, in which case the openings 16 are omissible. Further, the arms 13 and 15 may be raised to extend in the opposite direction to the direction as shown in FIG. 2, that is, such that the arms 13 extend in the same direction as the insertion direction of the pins 3 and the arms 15 extend in the same direction as the insertion direction of the pins 8. If desired, the arms 13 and 15 may even be so formed as to extend in the same direction. In these modifications, the configurations of the two housing 5 and 11, the configurations and lengths of the respective pins should be changed in matching relation to the direction in which the arms 13 and 15 extend. 
     Referring to FIG. 4, a general construction of the connector 1 in accordance with the present invention is shown in a perspective view with the bores 4 facing upward. In the figure, dash-and-dot lines shown that the bores 4 having the same configuration are positioned in arrays. Coaxial pins are inserted from above into the bores 4 while, at the same time, the same number of signal pins and ground pins as the coaxial pins are inserted from below into the connector 1, whereby electrical connection is established as described earlier with reference to FIGS. 2 and 3. 
     In the specific construction shown in FIG. 4, the connector 1 is divided into four blocks I, II, III and IV. This is to prevent, for example, the coaxial pins from failing to be inserted between their associated resilient arms 13 due to errors particular to various kinds of machining such as forming the housings 5 and 11 and cutting and raising the plate 12. If the connector 1 is not divided into blocks and the plate 12 is implemented by a single elongate plate, those errors would accumulate to bring about the above-described insertion failure in a part of the connector 1. In the first embodiment, the connector 1 is made up of a plurality of blocks each including one short metal plate 12. Dividing the connector into four blocks as shown and described is only illustrative. The gist is that one block be shorter than a particular length which is determined on the basis of the above-described errors, a mounting accuracy required and so on. 
     Referring to FIG. 5, a second embodiment of the invention is shown which comprises a thin metal plate 112 in place of the thin metal plate 12 of FIGS. 2 and 3. As shown, the plate 112 is cut and raised to form resilient arms 113 at its positions for receiving the coaxial pins 3 (FIG. 2). A coaxial pin contact 117 is provided for interconnecting any of the pins 3 and its associated signal pin 7 (FIG. 2) through an opening 114 which is formed between the arms 113. The plate 112 is also cut and raised to form another group of resilient arms 115 at its positions for receiving the pins 8 (FIG. 2). A ground pin contact 118 is provided in which any of the pins 8 is inserted through an opening 116 of the plate 112. 
     In the second embodiment, upper portions of the resilient arms 113 are further cut and raised to form pawls 113a. In this configuration, when any of the pins 3 is inserted into the opening 114, the pawls 113a of the arms 113 snap into the recesses 3b of the pin 3 and in the resulting position prevent the pin 3 from slipping out of the connector 1 except when the pin 3 is intentionally pulled with an extraordinary force. In this manner, the pawls 113a help their associated resilient arms 113 surely retain the pin 3 within the connector 1. 
     While this invention has been described in conjunction with the preferred embodiments thereof, it will now readily be possible for those skilled in the art to put this invention into practice in various other manners.